Undersealing caravans?

[AlanD_5039797]

In view of the recent snowy weather in some parts of the country lately,and the inevitable gritting of the roads, is it worthwhile undersealing a caravan to provide extra protection to the underneath of a caravan? Your thoughts please.

 

[JTQ]

I chose to treat the chasis with "Supertrol" an automotive rust inhibitor similar to Waxoyl as the salt will strip the zinc galvanising; and it works for me. On an earlier aluminium chasis van I also successfully used this same product

I dont touch the ply underfloor. Nor do I use the inhibitor in areas where there is a risk of getting it on or near sealant as it breaks this down.

 

[vernon]

My (Avondale) handbook says the wood floor should NOT be treated with anything.

 

[Carlton1]

Alan.

I'd keep away from using car underseal, as this will get hair line cracks from stones, then water will get underneath and rot will start, just like it does on cars. Hope this helps.

Carlton.

 

[Steve L]

Aluminimum provides it's own barrier to corrossion by actully oxidizing it's surface. So underseal is not realy the answer.

The wood floor is left un coated to allow it to breath, by sealing it you may well induce a faster natural deterioration process, ie cause the laminate to sweat.

Good old WD40 sprayed on the aluminium won't do any harm and will afford a bit of protection. We use a synthetic sylicone spray called "coolmax" at work to assist in stretch forming Lotus elise chassis rails which coats the aluminium in a slippery coating to protect the material from scratching.

The manufacturer is based at Wrexham north Wales.

Steve.

 

[rob_jax]

Free chemistry advice:

The modern caravan chassis is made from hot dipped (pre-formed steel dipped into molten Zinc) galvanised steel. When really fresh and new, the surface should shine and you may also see penny sized zones in the Zinc surface - this is all well and good.

Over a few months or even years (depending on the weather, temperature, etc), the Zinc surface slowly oxidises and forms a matt (mid grey) protective layer - this resistant layer protects the Zinc and the steel underneath.

Road salt doesn't affect the Zinc Oxide layer, but if it can get at the bare Zinc metal underneath - then it will attack that and eventually expose the steel - and then you'll see rusting start.

If you are out on salted roads - wash the chassis once the weather has warmed up.

You can further protect the Zinc with Waxoyl type DIY treatments, but it doesn't really need it.

If the Zinc surface develops a "fuzz" don't worry, it's just an extra thick layer of protective Zinc Oxide - it may look unsightly - but don't remove it.

Thoughts on WD40: As a chemist / chemical engineer with two university degrees, and 30 years experience in petrochemicals - let me say that it is an odourless paraffin oil with a fragrance - it evaporates and soon disappears. If you want to spray expensive "Esso Blue" over everything, then go ahead, it won't (or shouldn't) hurt.

Thoughts on a modern caravan floor: Our Eriba floor is a standard plywood / foam / plywood bonded sandwich, with a bottom breathable membrane and protective coat. If you have this type of floor, don't cover it with any sealant - it needs to breath.

Attempts in the 1970's to seal Eriba floors with an all-round waterproof coating were not successful - many 60's Eribas have their original plywood floor and all 1980's onwards will be original - but probably not those from the 70's. It's nice to have a group of long lived caravans on hand - then you can look back at what was a "good idea" 30+ years ago and see if it really was.

Robert

 

[JTS]

I think most of the comments have got it right about the chassis. no treatment required, One more thing though - car underseal is not intended for wooden floors (probably bituem based) and it would probally be absorbed by the wood and may eventually seep through.John.

 

[cris_408518]

In the past we've bought used caravans after very carefuly checking for damp problems etc. We also have an in family budget caravan doer upper who has bought vans cheap and rebuilt the dodgy parts for himself and others. He's found on a number of vans over many years that problems re sagging or delaminating floors often arise as flexing between the chassis and the floor allows water to penetrate where the floor is fixed to the chassis. Points such as side steadies screwed into the floor and brackets for pipes and cables, clamps and in floor vents and vent covers can also lead to floor problems expecially if you get a good lot of mud build up that sticks to the underside of the van.

Taking his advice I get the van jacked up and give the uderneath a very thorough clean and seal along the chassis rails where they meet the floor with Sikaflex to prevent water getting between chassis and floor and all edges get the same treatment and also around the wheel arch box's. In the past we've found flimsy GRP arch surrounds that hide bare wood of the caravan frame so it was worth having a look around.

We've had electrical problems in the past due to poor earthing. The earthing point has been drilled through the newly galavanised chassis and after some time the hole starts to rust so I make sure that area and all the vents ets are treated.

Some vans have the bottom forward facing curve of the GRP back wall that acts like a scoop for rain water spray off the wheels with loads of space for water absorbing muck to collect quite high up. Spray foam cures that area being a collection point and laquer on some rough feeling floors also stops muck from sticking to them.